41

Describe the relation between Resonance
power and off resonance power.


 The off resonance power = P / (
1 + Q^{2} )
Where P = Power at resonance
and Q = Tangent of the circuit
Phase angle
 The off resonance power is
reduced by factor ( 1 + Q^{2} ) to that of resonance power.

42

Explain the following terms:
Impedance, Admittance, Conductance, Inductive reactive, Inductive susceptance,
Capacitive reactance and Capacitive
susceptance


Impedance
( Z )
 It is defined as the combined
effect of resistance and (inductive or capacitive) reactance. Its unit is
ohm.
Z = r + j X_{L}
OR
Z = r – j X_{C}
Admittance
( Y )
 The reciprocal of impedance is
called as admittance. Its unit is Siemens.
Y = 1 / Z
Conductance
( G )
 The reciprocal of resistance is
called as conductance.
 Its unit is ohm^{1}.
G = 1 / R
Inductive
reactive ( X_{L })
 The opposition offered by the
inductance to the flow of current is called as inductive reactance.
 It is donated by X_{L}
= 2πfL
Inductive Susceptance ( B_{L })
 The reciprocal of inductive
reactance is called as inductive susceptance.
 The inductive susceptance is
taken as negative because the inductive reactance is taken as positive.
B_{L}=1 / X_{L}
Capacitive
reactance ( X_{C })
 The opposition offered by the
inductance to the flow of current is called as inductive reactance.
 It is donated by X_{C}
= 1 / 2πfC
Capacitive
susceptance ( B_{C })
 The reciprocal of capacitive
reactance is known as capacitive susceptance.
 The capacitive susceptance is
taken as positive because the capacitive reactance is taken as negative.
B_{C }=1 / X_{C}

43

At which condition the
conductance is reciprocal of resistance and susceptance is reciprocal of
inductive reactance in the series RL circuit?


Impedance
of series RL circuit
= R + jX_{L}
= ( R + jX_{L} ) / ( R^{2 }+ X_{L}^{2
})
= [ R / ( R^{2 }+ X_{L}^{2
})] + j [ X_{L} / ( R^{2 }+ X_{L}^{2 })]
= G + jB
Therefore
G = [ R / ( R^{2 }+ X_{L}^{2
})]
B = [ X_{L} / ( R^{2 }+ X_{L}^{2
})]
 When the inductive reactance
becomes zero, the conductance is reciprocal of resistance.
 Similarly when the resistance
becomes zero, the susceptance is reciprocal of inductive reactance.

44

Describe the condition for Parallel Resonance.


Parallel Resonance
 The circuit is called as
parallel resonance when the net reactance of the circuit becomes zero.

45

Define : Series Resonance Frequency


Series Resonance Frequency
 It is frequency at which net
reactance of the circuit becomes zero.
f_{r }= 1 / 2π √ ( LC )

46

Define : Parallel Resonance Frequency


Parallel Resonance Frequency
 It is frequency at which net
reactive component of the circuit becomes zero.
f_{r} = √ [( 1 / LC ) –
( R^{2} / L^{2} )]

47

Give reason : The parallel
resonance circuit is called as rejector circuit.


Rejector circuit
 The parallel resonance circuit
is called as rejector circuit because it rejects that frequency with it
resonates.

48

Give reason : The parallel
resonance is also referred as current resonance.


Current Resonance
 The parallel resonance is
called as current resonance because current circulates between two parallel
branches is much higher than the supply current.

49

Describe the effect of
frequency on the susceptance of the parallel resonance circuit.


Capacitive Susceptance
 It is directly proportional to the
applied frequency. As the frequency increases, the capacitive susceptance
increases.
Inductive Susceptance
 It is inversely proportional to
the applied frequency. As the frequency increases, the inductive susceptance
decreases.

50

Explain the term : Q factor of
parallel circuit


Q factor of Parallel circuit
 It is defined as the current
circulating between two parallel branches to the supply current.

51

Describe the significance of Q
factor in the series resonance circuit and parallel resonance circuit.


Significance
of Q factor
 The Q factor in the series
resonance indicates voltage magnification whereas it indicates current
magnification in the parallel resonance circuit.

No comments:
Post a Comment